David Cameron would get support for European Union (EU) reform if he did more to solve the unprecedented refugee and migrant crisis and the continued debt burden, it has been claimed.

Former taoiseach John Bruton accused the prime minister of badly timing his campaign, claiming the UK had excluded itself from tackling the two big problems facing modern Europe.

Mr Cameron has put restricting benefits for migrants at the heart of his demands, a move which Mr Bruton suggested would carry little support in Dublin with Britain still a popular destination for Irish workers.

"The impact on the EU itself of a possible UK exit is incalculable," he said.

"So also are the effects of the precedent the UK is setting and the consequences for the EU of conceding some of the UK requests.

"Solving this politically-generated problem will require statesmanship and imagination of a very high order indeed. Keeping the UK in the EU is a vital matter for Ireland and for Europe."

Mr Bruton, a former EU ambassador to the US, previously said Brexit would play into the hands of criminals, right-wing extremists and Vladimir Putin.

In his second speech on the risk of a Brexit in as many months, he told a seminar organised by the Institute of European Democrats in NUI Maynooth that the "timing of this renegotiation is bad", with the migrant and refugee crisis deepening and national debt issues remaining.

"A supportive attitude by the UK on the resolution of these EU-wide problems would help create the impression that the UK is, potentially at least, in the EU for the long haul, which would make it worthwhile for other members to go all the way to their bottom lines in attempting to meet the UK's requests," Mr Bruton said.

The biggest concern in Dublin follows an influential think-tank's assessment that Brexit would see Irish exports fall by three billion euro a year.

The European Commission has described Mr Cameron's agenda as having "some feasible elements, some difficult and some highly problematic".

Aside from reform on migrants' access to benefits, Mr Cameron said the UK should also be exempted from the commitment to "ever-closer union", get protection from eurozone integration and see improvements in competitiveness.

A key issue is a proposed four-year bar on access to in-work benefits and housing.

Mr Bruton said that runs counter to EU rules on the free movement of workers and he also suggested restricting tax credits would hit incomes.

"It would presumably apply to Irish workers in the UK who have been there for less than four years. It will be difficult for an Irish government to consent to this," the former Irish leader said.

Mr Bruton said he supports efforts for increased c ompetitiveness.

But he warned about allowing a " sovereignty veto" to give national parliaments the power to come together to stop some EU laws.

"This idea that a minority could block a majority would alter the entire dynamic of EU decision-making. It would make it hostage to the vagaries of national electoral politics in a new and unpredictable way," Mr Bruton said.

He also claimed contradictions in the reform proposals such as seeking more flexibility for member states but then making the UK's position on some issues irreversible.

"The UK already has special arrangements on the euro, on passport controls, and on justice and home affairs. The more exemptions it gets, the more exemptions it seems to want," he added.